The invention relates to a method and device for encoding an information stream that is organized as a sequence of pictures.
The processing of digital audio and video, such as for transmission or for storage, has necessitated the use of various data compression technologies. A non-limiting example is the MPEG standard, that has various versions for audio as well as for video.
Another standard is H.261. Realizing such compression in software has been disclosed in Ho-Chao Huang et al, New Generation of Real-Time Software-Based Video Codec: Popular Video Coder II, IEEE TR. Cons.El. Vol.42, No.4, P.963-973. It is feasible to have compression and similar operations executed in a mixed software and hardware environment. The number of operations required for encoding through software is difficult to predict. An embodiment hereinafter will be mainly described with reference to video. Now generally, the compression is executed on the basis of Groups of Pictures (GOPs). Hereinafter, the term xe2x80x9cpicturexe2x80x9d will be used consistently. Depending on the actual video standard, the term xe2x80x9cpicturexe2x80x9d may mean xe2x80x9cframexe2x80x9d as well as xe2x80x9cfieldxe2x80x9d. Now, the compression of frame-wise organized audio or mixed audio/video information streams may be effected in similar manner. Such processing must be done in real-time, which implies that a high penalty must be paid in case of processor overload, by loosing pictures or parts thereof.
Such compression has been proposed on the basis of so-called Intra-pictures, Predictive-pictures and Bidirectional predictive pictures.
The inventors have recognized the non-uniform processing efforts that are necessary for these three pictures categories. They have also recognized various tradeoffs that could be made among these categories for improving processing throughput whilst maintaining encoding quality.
In consequence, among other things, it is an object of the present invention to systematically suppress certain elements of the conventional processing to alleviate processing load. Now therefore, according to one of its aspects, the invention is characterized as recited in the characterizing part of claim 1. The invention also relates to an encoder arranged for implementing a method according to the invention. Further advantageous aspects are recited in dependent Claims.
These and further aspects and advantages of the invention will be discussed more in detail hereinafter with reference to the disclosure of preferred embodiments.